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The size of the cells selected was 57 J. 90 ft in th~ ~ast-west (X) direction and
510.28 ft in the north-soutll (Y) direction. This panicular grid size was selected to
coincide with the exact position of the north and east sidelines of the WIPP Site. This
assisted in panitioning the reserve' summations to determine tonnages inside and outside
the WIPP boundaries. The cell size selected resulted in the assignment of 60 cells in the
east-west direction and 63 in the north-south direction, for a total of 3780 cells. The
dimensions of an individual cell results in the ability to assign individual thickness and
grade to 58,OOO-tmrblocks of in-place ore 3 ft thick (a typical thickness).
Definition of the gridded (study) area. A feature of the MacGridzo program is
the placement of a rectangular boundary based on the extremity coordinates of the data
set. Hole No. U-134 determined the northern, Hole P-20 the easte-·:. Hole No. P-16 the
southern, and Hole No. D-48 the western boundary of the gridde... "rea. Resource.
tonnages and gri!-des could be estimatell.within that rectangle. Therefore, on labels for
maps and tables the term "Entire Gridded Area" was used to defme calculations within
that boundary. In the text, this is referrelfto as the "Study Area. "
Separation of the WIPP area from the study area. It was then a simple procedure
to clip the gridded cell information along the WIPP boundanes. This allowed the
calculation of resources for the entire study area and the WIPP boundary area. The
simple difference in the two resulted in defIDing resources outside of WIPP.
VII-8
Initial calculation of in-place resources. The initial step in calculating the
resources was determining the actual in-place tODLes in grade ranges using only the
actual thicknesses.and assays for each ore intercepl ;eported in the drill-hole records. The
fIrst procedure was.to de~rmine the thicknesses for each cell using the radial search
method. Second, assay results for % K 2 0 as langbeinite, sylvite (or equivalent mixture
using the 2.5:1 ratio) were assigned in a similar manner to each cell. The third step was
to determine the "thickness x grade product." Once these three steps were completed, a
contour map was produced for: thickness, grade, and product of thickness x grade.
These maps gave a visual presentation of the actual ore resources in-place without
consid~rationfor the need to correct for mining height-a step that would be needed to
determine the viability of mining.
The product maps (grade x thickness) provided an essential element for determining
what portion of the resources would become reserves. To illustrate, the BLM uses
the criterion of 4 ft of 10%..K 2 0 as sylvite to determine Lease GJ::llde Reserves.
Therefore, the product of thickness x grade is 40. This criterion is not dependent on
thickness or grade but the product of the two. Of course one always has to back in the
criterion that the grade will be at least 10% K 2 0 for sylvite (or 4% for langbeinite) if the
thickness is less than 4 ft. This latter criterion was readily determinCd by examination of
the contour map of grade. 'I1ieadvantage ofthe product contOur maps is that one can
readily determine the: outer boundaries for any specific definition of reserves, e.g., the 40
contour is the boundary for Lease Grade Svlvite Reserve...
The resource tonnages could then be determined by calculating the volume of each
cell which was multiplied by the "Tonnage Factor." For sylvite ores we used a constant
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